Nadia starts counting at 45, and she counts by fives. If 45 is the 1st number that Nadia counts. what is the 15th number that she counts?
Solution: What is the first number that she counts? $45$ What is the second number that she counts? $\begin{align*}&45 + 5 \\ &= 50\end{align*}$ What is the third number that she counts? $\begin{align*}&45 + 5 + 5 \\ &= 45 + (2 \times 5) \\ &= 55\end{align*}$ What is the 15th number that she counts? $\begin{align*}&45 + (14\times5) \\ &= 45 + 70 \\ &= 115\end{align*}$